U.S. patent application number 13/864341 was filed with the patent office on 2014-06-12 for impact-type piezoelectric micro power generator.
This patent application is currently assigned to Electronics and Telecommunications Research Institute. The applicant listed for this patent is ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE. Invention is credited to Kwang-Seong Choi, Chi Hoon JUN, Sang Choon Ko, Seok-Hwan Moon.
Application Number | 20140159547 13/864341 |
Document ID | / |
Family ID | 50880191 |
Filed Date | 2014-06-12 |
United States Patent
Application |
20140159547 |
Kind Code |
A1 |
JUN; Chi Hoon ; et
al. |
June 12, 2014 |
IMPACT-TYPE PIEZOELECTRIC MICRO POWER GENERATOR
Abstract
The present inventive concept discloses an impact-type
piezoelectric micro power generator. The impact-type piezoelectric
micro power generator may comprise a base having a cavity and at
least one stop area adjacent to the cavity; a frame fastened to the
base; a vibrating body comprising a plurality of first vibrating
beams extended from the frame toward a top of the cavity, an impact
beam connected to between first tips of the plurality of first
vibrating beams and extended onto the stop area, and a second
vibrating beam extended from the impact beam to between the
plurality of first vibrating beams, the second vibrating beam
having a second tip; and a piezoelectric device disposed on one of
a top and a bottom of the second vibrating beam and the impact
beam, the piezoelectric device generating electric power according
to impacts of the vibrating body to the stop area and bending of
the impact beam and the second vibrating beam.
Inventors: |
JUN; Chi Hoon; (Daejeon,
KR) ; Ko; Sang Choon; (Daejeon, KR) ; Moon;
Seok-Hwan; (Daejeon, KR) ; Choi; Kwang-Seong;
(Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELECTRONICS AND TELECOMMUNICATIONS RESEARCH INSTITUTE |
Daejeon |
|
KR |
|
|
Assignee: |
Electronics and Telecommunications
Research Institute
Daejeon
KR
|
Family ID: |
50880191 |
Appl. No.: |
13/864341 |
Filed: |
April 17, 2013 |
Current U.S.
Class: |
310/339 |
Current CPC
Class: |
H02N 2/186 20130101;
H01L 41/1136 20130101 |
Class at
Publication: |
310/339 |
International
Class: |
H02N 2/18 20060101
H02N002/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2012 |
KR |
10-2012-0141031 |
Claims
1. An impact-type piezoelectric micro power generator comprising: a
base having a cavity and at least one stop area adjacent to the
cavity; a frame fastened to the base; a vibrating body comprising a
plurality of first vibrating beams extended from the frame toward a
top of the cavity, an impact beam connected to between first tips
of the plurality of first vibrating beams and extended onto the
stop area, and a second vibrating beam extended from the impact
beam to between the plurality of first vibrating beams, the second
vibrating beam having a second tip; and a piezoelectric device
disposed on one of a top and a bottom of the second vibrating beam
and the impact beam, the piezoelectric device generating electric
power according to impacts of the vibrating body to the stop area
and bending of the impact beam and the second vibrating beam.
2. The impact-type piezoelectric micro power generator of claim 1,
wherein the frame has a shape of one of a loop and a ring
surrounding the cavity of the base.
3. The impact-type piezoelectric micro power generator of claim 2,
wherein the stop area of the base is disposed in the frame having
the shape of one of the loop and the ring.
4. The impact-type piezoelectric micro power generator of claim 3,
wherein the stop area is overlapped with both ends of the impact
beam of the vibrating body and disposed below the impact beam.
5. The impact-type piezoelectric micro power generator of claim 3,
wherein the stop area is disposed below one of the plurality of
first vibrating beams and the impact beam.
6. The impact-type piezoelectric micro power generator of claim 3,
wherein the stop area is disposed to traverse the cavity.
7. The impact-type piezoelectric micro power generator of claim 1,
wherein the piezoelectric device is disposed on one of a top and a
bottom of a part of the second vibrating beam and generates
electric power according to bending of the second vibrating
beam.
8. The impact-type piezoelectric micro power generator of claim 1,
wherein the piezoelectric device is disposed on one of a top and a
bottom of a part of the impact beam and generates electric power
according to bending of the impact beam.
9. The impact-type piezoelectric micro power generator of claim 1,
wherein the piezoelectric device comprises one of a piezoelectric
unimorph, a piezoelectric bimorph, and a piezoelectric
multimorph.
10. The impact-type piezoelectric micro power generator of claim 9,
wherein the piezoelectric unimorph comprises: a lower electrode
disposed on one of the second vibrating beam and the impact beam; a
piezoelectric body disposed on the lower electrode; and an upper
electrode disposed on the piezoelectric body.
11. The impact-type piezoelectric micro power generator of claim
10, wherein the piezoelectric body comprises at least one of an
inorganic material, an organic material, and a mixture thereof.
12. The impact-type piezoelectric micro power generator of claim
10, further comprising: at least one wiring electrically connected
to one of the upper electrode and the lower electrode of the
piezoelectric device and the frame; and at least one pad
electrically connected to the wiring and disposed on the base.
13. The impact-type piezoelectric micro power generator of claim
10, wherein the lower electrode is fastened to the vibrating body
by using one of an adhesive and a deposited film.
14. The impact-type piezoelectric micro power generator of claim
13, wherein the adhesive comprises one of conductive epoxy and
insulating epoxy.
15. The impact-type piezoelectric micro power generator of claim 1,
further comprising a mass adjacent to the piezoelectric device and
fastened to the second tip of the second vibrating beam to control
a frequency response of the vibrating body.
16. The impact-type piezoelectric micro power generator of claim 1,
further comprising a lid covering the vibrating body to restrict a
moving distance of the vibrating body above the base or protect the
vibrating body.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This U.S. non-provisional patent application claims priority
under 35 U.S.C. .sctn.119 of Korean Patent Application No.
10-2012-0141031, filed on Dec. 6, 2012, the entire contents of
which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The present inventive concept disclosed herein relates to a
piezoelectric power generator generating power by itself, and more
particularly, to an impact-type piezoelectric micro power
generator.
[0003] Portable electronic devices generally used in daily lives or
production environments may include a battery or a fixed power
supply as a power source. Particularly, in the case of batteries,
it is necessary to periodically charge or exchange according to
lifespan thereof. Maintenance cost occurs when changing batteries,
and environmental pollution is generated when disposing them.
Accordingly, recently, instead of power sources including batteries
or fixed power supplies, necessity of self-powered electronic
devices generating power by itself and operating has been
increased. Particularly, as sensing and monitoring devices have
been developed to be wireless and to consume low power, it is
necessary to develop micro power generators capable of supplying
power by using an energy harvesting principle collecting or
harvesting electric energy from surrounding environments. These may
have a modular form or a single body shape and may be used for
electronic devices function as independent power sources or
emergency power sources.
[0004] Micro power generation using energy harvesting may have
great technical and economical effects when being used in places in
which environmental energy always exist, for example, vehicles,
motors, railways, flights, roads, bridges, air conditioning
systems, and automated production lines. For example, a tire
pressure monitoring system (TPMS) that is a wireless sensor module
monitoring a pneumatic tire pressure state in real time may be
installed together with a micro power generator. In this case, the
micro power generator converts mechanical energy generated in the
tire into electric energy to provide power to the wireless sensor
module for the vehicle without using an external power supply
unit.
[0005] Piezoelectric micro power generators may convert physical
energies such as vibrations, impacts, rotational forces, inertial
forces, pressure, and fluid flows into electric energies. Mostly,
as energy converting materials of piezoelectric micro power
generators, piezoelectric materials are used. Piezoelectric
materials may generate electrical charges when mechanical strain
applied to the piezoelectric body. Accordingly, electrical charges
are collected by using electrodes, thereby generating electric
energies.
SUMMARY OF THE INVENTION
[0006] The present invention provides an impact-type piezoelectric
micro power generator having a simple configuration, generating
electric energy with high efficiency, and having high
reliability.
[0007] Embodiments of the inventive concept provide an impact-type
piezoelectric micro power generator comprising a base having a
cavity and at least one stop area adjacent to the cavity; a frame
fastened to the base; a vibrating body comprising a plurality of
first vibrating beams extended from the frame toward a top of the
cavity, an impact beam connected to between first tips of the
plurality of first vibrating beams and extended onto the stop area,
and a second vibrating beam extended from the impact beam to
between the plurality of first vibrating beams, the second
vibrating beam having a second tip; and a piezoelectric device
disposed on one of a top and a bottom of the second vibrating beam
and the impact beam, the piezoelectric device generating electric
power according to impacts of the vibrating body to the stop area
and bending of the impact beam and the second vibrating beam.
[0008] In some embodiments, the frame may have a shape of one of a
loop and a ring surrounding the cavity of the base.
[0009] In other embodiments, the stop area of the base may be
disposed in the frame having the shape of one of the loop and the
ring.
[0010] In still other embodiments, the stop area may be overlapped
with both ends of the impact beam of the vibrating body and
disposed below the impact beam.
[0011] In even other embodiments, the stop area may be disposed
below one of the plurality of first vibrating beams and the impact
beam.
[0012] In yet other embodiments, the stop area may be disposed to
traverse the cavity.
[0013] In further embodiments, the piezoelectric device may be
disposed on one of a top and a bottom of a part of the second
vibrating beam and generates electric power according to bending of
the second vibrating beam.
[0014] In still further embodiments, the piezoelectric device may
be disposed on one of a top and a bottom of a part of the impact
beam and generates electric power according to bending of the
impact beam.
[0015] In even further embodiments, the piezoelectric device may
include one of a piezoelectric unimorph, a piezoelectric bimorph,
and a piezoelectric multimorph.
[0016] In yet further embodiments, the piezoelectric unimorph may
include a lower electrode disposed on one of the second vibrating
beam and the impact beam, a piezoelectric body disposed on the
lower electrode, and an upper electrode disposed on the
piezoelectric body.
[0017] In much further embodiments, the piezoelectric body may
include at least one of an inorganic material, an organic material,
and a mixture thereof.
[0018] In still much further embodiments, the impact-type
piezoelectric micro power generator may further include at least
one wiring electrically connected to one of the upper electrode and
the lower electrode of the piezoelectric device and the frame, and
at least one pad electrically connected to the wiring and disposed
on the base.
[0019] In even much further embodiments, the lower electrode may be
fastened to the vibrating body by using one of an adhesive and a
deposited film.
[0020] In yet much further embodiments, the adhesive may include
one of conductive epoxy and insulating epoxy.
[0021] In yet much further embodiments, the impact-type
piezoelectric micro power generator may further include a mass
adjacent to the piezoelectric device and fastened to the second tip
of the second vibrating beam to control a frequency response of the
vibrating body.
[0022] In yet much further embodiments, the impact-type
piezoelectric micro power generator may further include a lid
covering the vibrating body to restrict a moving distance of the
vibrating body above the base or protect the vibrating body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings are included to provide a further
understanding of the inventive concept, and are incorporated in and
constitute a part of this specification. The drawings illustrate
exemplary embodiments of the inventive concept and, together with
the description, serve to explain principles of the inventive
concept. In the drawings:
[0024] FIG. 1A is a top view illustrating an impact-type
piezoelectric micro power generator according to an embodiment of
the inventive concept;
[0025] FIG. 1B is a cross-sectional view illustrating the
impact-type piezoelectric micro power generator of FIG. 1A;
[0026] FIGS. 2A to 2C are top views illustrating examples of
arranging a stop area on a base of FIGS. 1A and 1B;
[0027] FIG. 3 is a graph illustrating a pattern of a waveform of an
output voltage generated by the impact-type piezoelectric micro
power generator of FIGS. 1A and 1B
[0028] FIG. 4 is a graph illustrating output characteristics of
electric energy at a resonance frequency when acceleration applying
an external vibration in a Z-axis direction is changed in the
impact-type piezoelectric micro power generator of FIGS. 1A and 1B,
shown in generated output power and an output voltage; and
[0029] FIG. 5 is a graph illustrating a result of measuring
characteristics of the impact-type piezoelectric micro power
generator of FIGS. 1A and 1B after performing a shock test of 1,500
G/0.5 ms thereon.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0030] Preferred embodiments of the inventive concept will be
described below in more detail with reference to the accompanying
drawings. The inventive concept may, however, be embodied in
different forms and should not be constructed as limited to the
embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the inventive concept to those
skilled in the art.
[0031] Also, in the drawings, for clear description, a part having
no connection with the description, like reference numerals
designate like elements throughout.
[0032] Throughout the description and the whole claims, when a part
"includes/comprises" an element, with no particularly contrary
mention, this means that the part may further include/comprise
another element, which does not mean an exclusion of other
elements.
[0033] When a part such as a layer, an area, a plate, etc is "on"
another part, this means not only being right on the other part but
interposing still another part therebetween. On the contrary, when
a part is "right on" another element, this means that there is no
other part therebetween.
[0034] FIG. 1A is a top view illustrating an impact-type
piezoelectric micro power generator 100 according to an embodiment
of the inventive concept, and FIG. 1B is a cross-sectional view
illustrating the impact-type piezoelectric micro power generator
100 of FIG. 1A.
[0035] Referring to FIGS. 1A and 1B, the impact-type piezoelectric
micro power generator 100 may comprise a vibrating body 120, a
piezoelectric device 140, a mass 180, a frame 130, and a base
260.
[0036] The vibrating body 120 may respond to an outer environment
and may generate a mechanical movement. The vibrating body 120 may
comprise a plurality of first vibrating beams 121 extended from the
frame toward a top of the cavity 210, an impact beam 123 connected
to between first tips of the plurality of first vibrating beams 121
and extended onto a stop area 220, and a second vibrating beam 122
extended from the impact beam 123 to between the plurality of first
vibrating beams 121. The plurality of first vibrating beams 121 may
have a first length L.sub.1 and a first width a. The second
vibrating beam 122 may have a second length L.sub.2 and a second
width b. The first length L.sub.1 is greater than the second length
L.sub.2. The impact beam 123 may have a third length L.sub.3 and a
third width c. The first vibrating beams 121, the impact beam 123,
and the second vibrating beam 122 may be connected in a folded
shape. When the second vibrating beam 122 moves, the first
vibrating beams 121 and the impact beam 123 may move while being
connected with one another. The first vibrating beams 121, the
impact beam 123, and the second vibrating beam 122 in the folded
shape may provide an effect of increasing the entire length thereof
in a small area. Accordingly, the vibrating body 120 may respond to
an external low vibration frequency. A response to vibration
frequency may be precisely controlled by adjusting the first to
third lengths L.sub.1, L.sub.2, and L.sub.3, the first to third
ling widths a, b, and c, and a thickness t.
[0037] The vibrating body 120 and the frame 130 are formed of at
least one of an inorganic material, an organic material, and a
compound thereof such as FR4, FR5, polyimide, PET,
polydimethylsiloxane (PDMS), ceramic, glass, metal, a metal alloy,
plastic, and silicon. The vibrating body 120 and the frame 130 may
have a thickness t of from about 10 to about 1,000 .mu.m.
[0038] The piezoelectric device 140 may comprise one of a
piezoelectric unimorph, a piezoelectric bimorph, and a
piezoelectric multimorph disposed above or below the second
vibrating beam 122 and the impact beam 123. The piezoelectric
device 140 of the piezoelectric unimorph may comprise a lower
electrode 150, a piezoelectric body 160 on the lower electrode 150,
and an upper electrode 170 on the piezoelectric body 160. The
piezoelectric multimorph may be disposed not only above the
vibrating body 120 but below the vibrating body 120. The lower
electrode 150 and the vibrating body 120 may be connected by an
adhesive 110 or a deposited film. The adhesive 110 may comprise one
of conductive epoxy and insulating epoxy. The lower electrode 150
may be electrically connected to the frame 130 due to being in
contact with the vibrating body 120. The lower electrode 150 and
the upper electrode 170 may comprise metal such as Ni, Ag, Al, Au,
etc. The lower electrode 150 and the upper electrode 170 may have a
thicknesses of from about 0.3 to about 10 .mu.m.
[0039] The piezoelectric body 160 may convert a mechanical
variation of the vibrating body 120 into electric energy. The
piezoelectric body 160 may comprise ceramic such as PZT, PZN-PT,
PMN-PT, PMN-PZT, BaTiO.sub.3, and PbTiO.sub.3, a metal nitride such
as AlN, a metal oxide such as ZnO, an organic material such as
PVDF, and a nano material such as a nano wire, and a nano tube. The
piezoelectric body 160 may have a thickness of from about 1 to
about 500 .mu.m.
[0040] The mass 180 may be disposed on a second tip that is a
terminal of the second vibrating beam 122 adjacent to the
piezoelectric body 160. The second vibrating beam 122 and the mass
180 may be fastened by using one of the adhesive 110 and a
deposited film. The mass 180 may comprise a metal having high
density, such as tungsten, and a compound thereof. Also, the mass
180 may comprise at least one of an inorganic material, an organic
material, and a compound thereof.
[0041] The impact-type piezoelectric micro power generator 100
controls a frequency response thereof by using mass adjustment of
the mass 180.
[0042] The base 260 may be formed of at least one of an inorganic
material, an organic material, and a compound thereof such as FR4,
FR5, polyimide, PET, polydimethylsiloxane (PDMS), ceramic, glass,
metal, a metal alloy, plastic, and silicon. The base 260 and the
frame 130 may be bonded to each other by using one of the adhesive
110 and a deposited film. The frame 130 may have one of a loop
shape and a ring shape surrounding the cavity 210 of the base
260.
[0043] The vibrating body 120 may be fastened to the base 260 by
the frame 130. The base 260 may have the cavity 210 and a stop area
220 adjacent to the cavity 210. The stop area 220 may be disposed
below inside the frame 130.
[0044] A width W of the cavity 210 is greater than the sum of the
first length L.sub.1 of the first vibrating beams 121 and the third
length L.sub.3 of the impact beam 123. The cavity 210 may allow the
vibrating body 120 to vibrate. A height h of the base 260 may limit
a maximum displacement of the vibrating body 120.
[0045] One or more of the second vibrating beam 122 and the impact
beam 123 of the vibrating body 120 may collide with the stop area
220 of the base 260. The stop area 220 may amplify a generation
amount of electric energy by causing impact strain to the vibrating
body 120. A basic mechanism thereof is that one of the second tip
that is one end of the second vibrating beam 122 and the mass 180
bonded thereto may vertically vibrate with an amplitude of
.+-..DELTA.. In this case, one of the impact beam 123 and a part of
the second vibrating beam 122 on another end may be decreased in
its vibration amplitude due to the stop area 220 and thus may
vertically vibrate with the smaller amplitude of .+-..delta. than
.+-..DELTA.. Accordingly, piezoelectric body 160 may generate high
electric energy due to applied impact strain. That is, a
vibration-induced impact is artificially caused on a part of the
vibrating body 120 by using the stop area 220, thereby increasing a
generation amount of electric energy.
[0046] Also, a part of the piezoelectric body 160 may be simply
disposed adjacent to the stop area 220 by the medium of one of the
impact beam 123 and the second vibrating beam 122 of the vibrating
body 120, thereby forming a free-supported end structure.
Accordingly, the piezoelectric body 160 may bear a severe operating
condition such as a great mechanical shock and may stably output
electric energy.
[0047] Pads 230 may be disposed on an edge of the base 260. The
pads 230 may be connected to a wire 240 withdrawn from the upper
electrode 170 of the piezoelectric device 140. The pads 230 may be
electrically connected to the frame 130 with a wire 250 and the
frame 130 may be electrically in contact with the lower electrode
150 of the piezoelectric device 140.
[0048] A lid (not shown) that is a cover limiting a moving distance
of the vibrating body 120 or protecting vibrating body 120 may be
additionally assembled to the base 260.
[0049] FIGS. 2A to 2C are top views illustrating examples of
arranging the stop area 220 on the base 260.
[0050] Referring to FIGS. 1A and 2A, the stop area 220 may be
overlapped with both terminals of the impact beam 123 of the
vibrating body 120 and may be located below the impact beam 123.
The stop area 220 may be disposed on edges of the cavity 210 of the
base 260.
[0051] Referring to FIGS. 1A and 2B, the stop area 220 may be
disposed below between the plurality of first vibrating beams 121
or the impact beam 123.
[0052] Referring to FIGS. 1A and 2C, the stop area 220 may be
disposed to traverse the cavity 210. The stop area 220 is not
limited to a certain shape and may be variously changed.
[0053] FIG. 3 is a graph illustrating a pattern of a waveform of an
output voltage generated by the impact-type piezoelectric micro
power generator 100.
[0054] To mimic an external environment, a vibration having a sine
waveform of 51.8 Hz in a Z-axis direction is artificially applied
to the impact-type piezoelectric micro power generator 100 by using
a vibration excitation system.
[0055] Referring to FIG. 3, the impact-type piezoelectric micro
power generator 100 generates an output voltage V.sub.pp having an
erratic waveform pattern. That is, the piezoelectric device 140
periodically generates high electric energy whenever the vibrating
body 120 collides with the stop area 220. In this case, the mass
180 vibrates with a frequency of 51.8 Hz with respect to a vertical
direction of the base 260 and the vibrating body 120 has a
thickness of 50 .mu.m. The piezoelectric body 160 of the
piezoelectric device 140 may comprise a PZT having a thickness of
127 .mu.m. The impact-type piezoelectric micro power generator 100
may generate a continuous output voltage denser than general simple
resonance-type piezoelectric micro power generators by using a
vibration-induced impact.
[0056] FIG. 4 is a graph illustrating output characteristics of
electric energy at a resonance frequency when acceleration applying
an external vibration in a Z-axis direction is changed in the
impact-type piezoelectric micro power generator 100, shown in
generated output power and an output voltage.
[0057] The entire area of the impact-type piezoelectric micro power
generator 100 used in the measurement may be about 20.times.20 mm,
and the vibrating body 120 may have an area of about 13.times.12 mm
and a thickness of about 50 .mu.m. The piezoelectric body 160 may
have an area of 37 mm.sup.2, and the mass 180 may have a weight of
0.62 g. A lid (not shown) that is a cover covering the vibrating
body 120 above the base 260 of the impact-type piezoelectric micro
power generator 100 is manufactured and assembled thereto in such a
way that a maximum moving distance of the vibrating body 120 is
limited to .+-.1 mm. A load resistance connected outside is
R.sub.L=2.98 k.OMEGA., and a resonance frequency is within a range
from about 50.2 to 64 Hz. In this case, 1 G=9.8 m/s.sup.2.
[0058] Referring to FIG. 4, electric power generated at the
resonance frequency shows linearity in a logarithmic scale
according to applied acceleration. Particularly, generated electric
power shows maximum/average values=1.18/1.09 mW in an excitation
condition of 1.4 G/62.3 Hz and 2.53/1.19 mW in a condition of 1.58
G/64 Hz, which are great values of about 1 mW or more. Accordingly,
the impact-type piezoelectric micro power generator 100 may provide
more electric power than a minimum value needed in general sensor
modules in spite of a micro structure, thereby providing a margin
in managing power sources.
[0059] Typically, general piezoelectric micro power generators have
been applied to fields of being used in a harsh external
environment such as TPMS systems. Accordingly, a mechanical shock
in a harsh condition is artificially applied to the impact-type
piezoelectric micro power generator 100, thereby estimating
operation reliability thereof. A mechanical shock using a shock
test system of Lansmont Corporation is applied with acceleration of
1,500 G for 0.5 ms in a Z-axis direction. The entire area of the
impact-type piezoelectric micro power generator 100 that has been
tested may be about 20.times.20 mm, and the vibrating body 120 may
have an area of about 13.times.12 mm and a thickness of about 100
.mu.m. The piezoelectric body 160 may have an area of 40 mm.sup.2,
and the mass 180 may have a weight of 0.62 g. A lid (not shown)
that is a cover covering the vibrating body 120 above the base 260
of the impact-type piezoelectric micro power generator 100 is
manufactured and assembled thereto in such a way that a maximum
moving distance of the vibrating body 120 is limited to .+-.1
mm.
[0060] FIG. 5 is a graph illustrating a result of measuring
characteristics of the impact-type piezoelectric micro power
generator 100 after performing a shock test of 1,500 G/0.5 ms on
the impact-type piezoelectric micro power generator 100.
[0061] Referring to FIG. 5, when an external load resistance is
R.sub.L=6.72 k.OMEGA., the impact-type piezoelectric micro power
generator 100 may have a vibration response of resonance frequency
of 124.3 Hz when acceleration applied in a Z-axis direction is
0.637 G. In this case, maximum/average values of generated electric
power are 767/456 .mu.W. Accordingly, the impact-type piezoelectric
micro power generator 100 may normally generate a resonance
frequency, an output voltage, and electric power after a harsh
condition was applied.
[0062] The impact-type piezoelectric micro power generator 100
shows characteristics designed to respond to a low vibration
frequency with a simple micro structure. Also, since high electric
power can be generated in spite of the micro structure due to a
vibration-induced impact, it is possible to satisfy an electric
power level needed in general wireless sensor modules. Also, since
electric energy can be normally generated after an external
mechanical shock in a harsh condition, high reliability may be
shown.
[0063] The impact-type piezoelectric micro power generator may
comprise a base, a frame, a vibrating body, a piezoelectric device,
and a mass. The base may comprise a cavity exposing the vibrating
body downwardly and a stop area adjacent to the cavity. The frame
may fasten the vibrating body to a circumstance of the cavity. The
vibrating body may comprise a plurality of first vibrating beams
extended from the frame toward a top of the cavity, an impact beam
connected to between first tips of the plurality of first vibrating
beams and extended onto the stop area, and a second vibrating beam
extended from the impact beam to between the plurality of first
vibrating beams having a second tip. The plurality of first
vibrating beams, the impact beam, and the second vibrating beam may
have a folded structure in the cavity. The piezoelectric device may
be disposed on one of a top and a bottom of the second vibrating
beam and the impact beam. The mass adjacent to the piezoelectric
device may be fastened to the second tip that is a terminal of the
second vibrating beam and may control a frequency response of the
vibrating body. The piezoelectric device may generate high electric
energy by using the vibrating body having the folded structure and
colliding the vibrating body with the stop area.
[0064] Accordingly, the impact-type piezoelectric micro power
generator, with the simple structure, may generate electric energy
with high efficiency and provide high reliability.
[0065] The above-disclosed subject matter is to be considered
illustrative, and not restrictive, and the appended claims are
intended to cover all such modifications, enhancements, and other
embodiments, which fall within the true spirit and scope of the
inventive concept. Thus, to the maximum extent allowed by law, the
scope of the inventive concept is to be determined by the broadest
permissible interpretation of the following claims and their
equivalents, and shall not be restricted or limited by the
foregoing detailed description.
* * * * *